In order that a receiver may synchronize, within a digital transmission system, to a digital signal sent out by a transmitter, the transmitter will radiate a digital signal known to the receiver. It is the receiver's task to determine the precise TOA (time of arrival) of the signal sent.
To determine the time of arrival, the cross-correlated between the digital receive signal and the known digital transmit signal is calculated.
In localization systems, a transmitter also emits a digital signal which will be received by several receivers. The position of the transmitter may be determined from the signal's times of arrival at the receivers via a run-time measurement.
On account of multipath propagation, in particular, the time of arrival of a signal can be determined in an imprecise manner only. In communication systems, for example, this leads to synchronization errors, or, in localization systems, to erroneous positioning.